Why a full medication list matters
Medicines can affect how your body responds to anaesthesia, your blood pressure, your blood sugar, your risk of bleeding and how quickly your stomach empties. To plan your anaesthetic safely, I need to know about everything you take, including:
- prescription medicines, including tablets, injections, inhalers, patches and eye drops;
- medicines bought from a pharmacy or supermarket, such as pain relievers and antihistamines;
- vitamins, fish oil, and herbal or traditional remedies, some of which affect bleeding or interact with anaesthetic medicines;
- weight-loss medicines, including those obtained online or through telehealth services;
- recreational drugs, cannabis and alcohol. This information is confidential and is asked for your safety.
The easiest way is to bring your medicines in their original packaging, or an up-to-date list from your GP or pharmacist, to your consultation and on the day.
Blood thinners
Blood thinners reduce the risk of blood clots. There are two main groups. Anticoagulants include warfarin, apixaban, rivaroxaban and dabigatran. Antiplatelet medicines include aspirin, clopidogrel, prasugrel and ticagrelor. People take them for reasons such as atrial fibrillation, previous clots, heart stents, heart valves or stroke prevention.
Before surgery, there are risks in both directions. Continuing a blood thinner can increase bleeding during and after some procedures, and can affect whether a spinal, epidural or some nerve blocks are safe. Stopping it can increase the risk of a clot, stroke or heart attack, and for some people, particularly those with recent heart stents, that risk can be serious.
Whether your blood thinner is continued, paused or replaced for a short time depends on why you take it, the specific medicine, your kidney function and the bleeding risk of your procedure. This decision is made together by your surgeon or proceduralist, your anaesthetist and the doctor who prescribed it, often your cardiologist, neurologist or GP. Some minor procedures can be done without stopping blood thinners at all.
Diabetes medicines
Surgery, fasting and anaesthesia can all affect blood sugar. Both high and low blood sugar can cause problems around the time of surgery, and good control helps with healing and recovery. If you have diabetes, please tell me which medicines you take, the doses, and how well your diabetes is usually controlled. A recent HbA1c blood test is helpful.
Insulin
Insulin is rarely stopped completely, because the body still needs some insulin even when fasting. The dose may need adjusting on the day before and the day of your procedure. You will be given individual instructions, sometimes in consultation with your endocrinologist or diabetes educator. Please do not change your insulin without this advice.
SGLT2 inhibitors
SGLT2 inhibitors include medicines such as empagliflozin, dapagliflozin and ertugliflozin, sometimes in combination tablets. They are used for diabetes, and also for heart failure and kidney disease. Around the time of surgery, especially with fasting, a low-carbohydrate diet or bowel preparation, they can cause a serious condition called ketoacidosis, where acids build up in the blood. This can happen even when blood sugar levels are normal or only slightly raised, which is why it is sometimes called euglycaemic ketoacidosis.
Australian guidance recommends that these medicines are usually paused for a short period before many procedures, and restarted once you are eating and drinking normally. The timing depends on the procedure, so you will be given specific advice. If you feel unwell with nausea, vomiting, abdominal pain or unusual tiredness in the days after a procedure, seek medical advice promptly.
Other diabetes medicines
Some tablets, such as metformin and sulfonylureas, may also need adjusting around a period of fasting. GLP-1 medicines are discussed in the next section.
GLP-1 and other weight-loss medicines
GLP-1 receptor agonists, and newer dual-action medicines, are increasingly used for type 2 diabetes and for weight loss. They include semaglutide (Ozempic, Wegovy), dulaglutide (Trulicity), liraglutide (Saxenda, Victoza) and tirzepatide (Mounjaro). They may be weekly injections, daily injections or tablets.
One of the ways these medicines work is by slowing how quickly the stomach empties. This means food can remain in the stomach for longer than usual, even after normal fasting. Under anaesthesia or sedation, that increases the risk of stomach contents entering the lungs (aspiration). Having no nausea or other stomach symptoms does not reliably mean the stomach is empty.
Current Australian recommendations
In April 2025, the Australian Diabetes Society, the Australian and New Zealand College of Anaesthetists, the Gastroenterological Society of Australia and the National Association of Clinical Obesity Services published updated clinical practice recommendations. In summary:
- Everyone having anaesthesia or sedation should be asked whether they take one of these medicines.
- Routinely stopping them before a procedure is generally not recommended, because stopping can worsen blood sugar and weight control, and it is uncertain how long a pause would be needed to make a difference. There may be individual exceptions.
- Instead, a clear-fluid-only diet for about 24 hours before the procedure is recommended, followed by the usual fasting period. This helps reduce what remains in the stomach, but cannot guarantee it is empty.
- "Sip Til Send" clear fluids up until theatre is generally not used for people taking these medicines. Fluid fasting instructions are usually stricter.
- People with diabetes, particularly those using insulin, need individual advice about the clear-fluid day, because it can affect blood sugar.
- Other factors that slow stomach emptying, such as some other medicines or conditions, are also considered. If the preparation has not been possible, your anaesthetist may take additional precautions, or the procedure may be rescheduled.
Other common medicines
Blood pressure and heart medicines. Most are continued, including on the morning of your procedure. Some, particularly ACE inhibitors and angiotensin receptor blockers, and some fluid tablets, may be withheld on the day, because they can cause low blood pressure under anaesthesia. You will be told which applies to you.
Steroids. If you take steroid tablets such as prednisolone regularly, or have taken them in recent months, please tell me. Your body may need additional steroid support around the time of surgery. Steroids should not be stopped suddenly.
The contraceptive pill and hormone replacement therapy. Some forms of oestrogen-containing medicines slightly increase the risk of blood clots after surgery. For many procedures they are continued, with measures to prevent clots. Decisions are individual, and depend on your procedure and other risk factors. Some medicines used during anaesthesia can reduce the effect of hormonal contraception for a few days. If this applies to you, your anaesthetist will let you know whether extra contraception is needed.
Medicines for mental health, epilepsy, Parkinson's disease and pain. These are usually continued, as stopping them can cause problems. Please make sure I know about them, including any long-term opioid pain medicines.
How your medication plan is made
Your medication plan is individual. It is based on your health, why you take each medicine, the procedure you are having and current guidance. It is usually agreed between your anaesthetist, your surgeon or proceduralist, and your GP or prescribing specialist, and explained to you in advance. If you receive conflicting instructions, or are not sure what to do, please ask before making any change.
Your medicines are also discussed as part of our consent conversation. See Understanding Your Anaesthetic & Informed Consent, and for general preparation, Preparing for Your Procedure.
Further reading
- GLP-1 receptor agonists: clinical practice recommendations (ANZCA)
- Clinical Practice Recommendations: Periprocedural Use of GLP-1RAs and GLP-1/GIPRAs, April 2025 (Australian Diabetes Society)
- Fasting before your surgery (ANZCA)